Refining nickel



Patented Mar. 19, 194 6 I I UNITED STATES PATENT OFFICE William J.Kroll. Niagara Falls, NY.

No Drawing. Application March 22, 1944,

Serial No. 527,668

Claims. (CI- -82) This invention relates to metallurgy and more totemperatures as low as 500 C..and as high as particularly to nickelmetallurgy and has for its 1000 C. in the presence of any one of themetals object the provision of a method of producing sub- Cu, Co, Fe,Cr, Zn and Mn, the nickel content of stantially pure nickel from finelydivided or comthe nickel chloride is progressively thrown out minutednickel containing relatively small 5 of chloride combination withformation of the amounts ofresidual impurities. chloride compound of themetal in contact there- Another object is to facilitate the productionwith, the progress of the reaction being one based of substantially purenickel. v 'on the relative rates of diffusion of the respective Stillanother object is to provide a method oi metals into each other and therates of diffusion processing nickel metal powder to eliminate there- 0of, the chlorides into each other, at any given from substantially allresidual impurities to obtemperature of heating.

tain thereby a high grade substantially pure nick- Therefore, by finelycomminuting both the metel metal powder product. I al and the nickelchloride, to reduce the diffusion Other objects will be apparent as theinvention paths to the smallest economically practical disis more fullyhereinafter disclosed. 5 tance and briquetting themived metal and chlo-In accordance with these cbjectsl have discovrides to bring theparticles into relatively close ered that when impure metallic nickel inits finely contact, the time factor may be lowered corredivided form' ismixed with nickel chloride Ispondingly and by employin a relativelylarge (NlCh) and the mixture is heated to elevated excess of nickelchloride over that theoretically, temperatures within the range 500 to1000 C. for required the rate of the reaction at any given an extendedtime interval, the metallic impuritemperature may be accelerated. tiespresent in the metallic nickel are in major In th adaptation of thisinvention commerpart converted into metal chloride compounds by cially,the most practical application of the same a displacement reactionbetween the contaminatappears to be in the treatment ofnickel metal ingmetal and the nickel chloride, the extent of powder to eliminatetherefrom from small persuch conversion being dependent upon metalparcentages down to substantially residual percentticle size, the amountand form of said impuriages of the metallic impurities Cu, Co, Fe, Cr,Zn ties, the temperature and time of heating and and Mn, present thereintherebyto obtainanickel other factors. w metal powder for sinteringheat-treatment to The-reaction involved in this invention is es- 80solid or coherent form that is of a relatively high sentially one ofdisplacement wherein the medegree of purity.

tallic impurity displaces the nickel of the nickel Heretofore in the artthe preparation of subchloride, the metal and chloride compounds eachstantially pure nickel has depended upon the being in the heated butsubstantially solid phase. practice of complex and expensivepurification Contrary to expectations based on allof the processespriortoreduction-ofthenickel compound data heretofore published, I havediscovered that to finely-divided metallic form. Even by ,the nickel isrelatively low in the displacement series practice of these complicatedand expensive in the system metal-metal chlorides at temperchemicalprocesses it is diilicult to obtain subatures within the range 500-1000C., and that stantially pure nickel. In accordance with the most of themetals commonly associated with (0 practice ofth present invention,however, the metallic nickel as difllcultly removed impurities, majorportion of the prior art complex and exsuch as Cu, Co, Fe, Cr, Zn andMn, lie above pensive chemical processes may be dispensed with nickel inthe said series and will displace nickel and a reduced'metal productconsisting mainly from nickel chloride at'some temperature within ofnickel and containing up to 2% metallic imthis range. puritiesconsisting of anyone or more of the met- The melting point of nickelchloride has not als Cu, Co, Fe, Cr, Zn and Mn, may be produced beenaccurately determined. The melting point which on comminuting torelatively small par- ,approximates 100l C. and the boiling pointapticle size, mixing with nickel chloride, briquetting proximates 975 C.When heated alone, nickel and heat-treating to temperatures within thechloride appears to vaporize just before melting range 500 to 1000C.,will b converted 'into sub-- and seems to have a melting point in theneighstantially purenickel. f Y v borhood of 1000" C. :As one specificembodiment-of the present in- Irrespective of this peculiarity of nickelchlovention, but not as a limitation thereof, the folride, I have foundthat when nickel chloride in lowing example maybe given: its anhydrousfinely divided solid form is heatedv Most nickel sulfide ores containcopper in various amounts, the complete separation of which from thenickel is difficult. Two main processes are at present in use, theOrford process based on the relative solubility of Cu and Ni sulfidesinsodium sulfide and the Mond process based on the volatility of nickelcarbonyl. Each of these processes are complicated and costly.

In accordance to the practice of the present invention the nickel andcopper content of the ore are isolated as metal oxides by methodsheretofore known in the art and the mixed metal oxides are reduced tometal powder by reduction in hydrogen, in accordance with well knownprior art practice, the reduction temperature preferably beingmaintained as low as possible to obtain as small a particle size aspracticable to handle sub sequently, in accordance with the presentinvention. Higher reduction temperatures may be employed, however, withno essential departure from the present invention as one skilled in theart will recognize,

The metal powder product obtained as above noted is screened to passabout 100 mesh screen, the over sized particles being rejected orcrushed and screened to pass 100 mesh, and is mixed with nickel chloride(anhydrous) also crushed to pass about 100 mesh, the relativeproportions of metal powder to nickel chloride being such as to providefrom 2 to 5 times the amount of nickel chloride theoretically requiredto obtain the substantially complete conversion of the copper content ofthe metal powder to copper chloride.

This mixture is then compacted to suitable sized aggregates or briquetsand the briquets are heated to temperatures approximating 700 C. for anextended time interval approximating one hour, in

an inert or substantially non-oxidizing atmosphere, such as pure drynitrogen, and the resulting sintered product is treated for theseparation of the metal powder from the mixed cuprous and nickelchloride present therein.

The reaction involved is essentially as follows:

particles.

The above heating may be practiced as a batch operation or as acontinuous operation, as one skilled in the art will perceive.

I have found that the heat-treatment of nickel metal powder containingup to 2% copper, in the manner described above, is effective to convertsubstantially all of the copper to cuprous chloride within a timeinterval of about one hour, using about 3 times the amount of NiClztheoretically required to accomplish this result. However, in

' the case of copper, the subsequent separation of the cuprous chloridefrom the purified nickel metal powder is rendered difiicult by reason ofthe fact that in aqueous chloride solution nickel lies above copper inthe displacement series. Accordingly, following sintering and conversionof the copper content of the metal powder to cuprous chloride (CuCl) theseparation of the nickel metal powder from the mixed copper and nickelchlorides by aqueous solutioning methods must be practiced with theshortest possible time interval of exposure of the metal powder to thedisplacement reaction (2CuCl-l-Ni=NiClz+Cu) which normally occur inaqueous solution.

sium chlorides the major portion of the copper chloride can be dissolvedout of the sinter and decanted away from the metal powder beforesubjecting the nickel powder to washing with water.

Substantially the same procedure may be fol lowed in separating from thenickel metal powder any of the metals Fe, Co, Cr, Zn and Mn. Iron andcobalt in amounts as high a 2% to 3% may be converted to chloridecompounds by the sintering heat-treatment of nickel metal powdercontaminated with these metals with nickel chloride in excess of theamount theoretically required at temperatures approximating 700 C. in asubstantially non-oxidizing and non-reducing atmosphere.

In practicing the present invention with solid coherent metal, themetal, if not of thin section, is first reduced to small particle siz byan convenient mechanical means. A particle size passing mesh has beenfound to be most suitable for the purposes of the present invention.Thin sectioned metal, such as turnings for example, usually need to bebroken up into small sized fragments having a size that is convenient tohandle.

It is believed apparent from the above description that the presentinvention may be widely varied without essential departure therefrom andall modifications and departures therefrom are contemplated as may fallwithin the scope of the following claims.

What I claim is: p

1. The method of treatingimpure nickel to remove therefrom associatedmetallic impurities wh ch comprises comminuting the nickel to relativelysmall particle size, mixing therewith anhy-' drous nickel chloride in anamount in relatively large excess of the amount required to react withsaid associated impurities, compacting the mixture and heating the saidcompacted mixture in an inert and substantially non-oxidizing atmosphereto elevated temperatures within the range 500 to 1000 C. for an extendedtime interval adapted to convert the major portion of the saidassociated metal impurities into metal chloride compounds by adisplacement reaction with said nickel chloride, and separating theresulting metal product from the chloride compounds associatedtherewith.

2. The method of claim 1, wherein the product of said heating isimmersed in a molten bath consisting of highly stable'metal chloridecompounds to separate the major portion of the metal chloride compoundstherefrom, and wherein the metal after separating the same from themajor portion of the said molten bath is washed with water to remove theremainder of the metal chlorides present therein.

3. The method of producing substantially pure adapted to obtain aconversion of the major portion or said metal impurities to chloridecompounds, cooling the sintered aggregates and sepaaggregates in amolten bath consisting of sodium and potassium chlorides to dissolve outthe major portion of said metal chloride compounds and wherein, afterseparating the major portion of the molten chloride bath from the saidmetal powder, the remaining chlorides are dissolved in water.

5. The method of treating cornminuted nick to extract therefrom any ofthe metals Cu, Co, Fe, Cr, Zn and Mn, associated therewith in relativelysmall total percentages, which comprises mixing the comminuted nickelwith anhydrous nickel chloride, the amount of said chloride being from 2to 5 times that theoretically required to convert the said associatedmetals into chloride compounds, compacting the mixture into convenientsized, briquets, heating the briquets in an inert atmosphere to atemperature approximating 700 C. for an extended itme interval adaptedto obtain a substantially complete conversion of the said associatedmetals to chloride compounds, cooling the heated'briquets and separatingthe metal product remaining from the chloride compounds associatedtherewith.

.WJLLIAM J. KROLL.

